Underexposing

[Chris P Nut]

I recently pulled focus for a DP who allways underexposed his images, almost to the degree that it was hard for me to see what was actually in focus. I asked him why he did this, and he said he pulls up the shadows in post because its more details in the blacks...

So, what is the advantage of underexposing (say 2 stops) instead of exposing "right"?

 

[Brandon Kraemer]

I recently pulled focus for a DP who allways underexposed his images, almost to the degree that it was hard for me to see what was actually in focus. I asked him why he did this, and he said he pulls up the shadows in post because its more details in the blacks...

So, what is the advantage of underexposing (say 2 stops) instead of exposing "right"?

Protecting your highlights. Once you burn out your highlights, that data is gone for good. You might expose "correctly" for your key but other brighter objects in the frame will burn. Unless your able to control your backgrounds very well, you can easily burn out details.

 

[Andrew Wilding]

On the MX ive done some tests shooting backlit stuff at 3200 iso. In the middle of the day. The image is remarkably clean and the highlight rim is not digitally clipped and so it rolls off smoother...

 

[Chris P Nut]

Sounds reasonable...

Is this method only doable on film and digital raw, or does some digital still cameras like the Canon 5D or 7D have enough details in the blacks?

 

[Andrew Wilding]

Well, you can underexpose a good deal on the 5d and presumably 7d and push it up in post - assuming you mean for raw stills. For h264 video though, I think you'd end up with severely noisy images...

 

[Chris P Nut]

Jupp, I'm talking about video...

 

[Dan Hudgins]

H.264

H.264

We did a filmout test of some H.264 shot in a Canon camera, when shot we underexposed about 1/2 to 1 stop to save the highlights.

The results looked good graded up except that the blocky artifacts also came up quite a bit because of the increase in midtone and shadow contrast.

We tried NeatVideo on the graded frames and when adjusted right it seemed to remove many of the "mosquito noise" artifacts.

Going from video rates to 24p may slow down the "mosquito noise" artifacts and make them look worse.

If you use temporal noise reduction like NeatVideo or ARRI Relativity you need to keep in mind motion artifacts, so try to use a tripod all the time and don't pan or tilt the camera, at least not in fits and jerks.

Going two stops down on H.264 would be something that you should shoot tests for before you try that on something important as the compression works for "finished" images and is does not have the same "pull up" range as real 12bit+ RAW data, perhaps.

If you want to hold your highlights by going 2 stops lower than the rim light, increase the fill light by at least a stop to a stop and a half then grade DARKER rather than lighter, you will have more data near the center of the compressed H.264 images, so its better to shoot with the light near the center of its range, perhaps. Also using an 80 series filter under low K light and using more fill can reduce sensor noise and what it adds to the "mosquito noise" artifacts.

 

[Chris P Nut]

wow, thanks Dan. That was really helpful, I will try that. Cheers!

 

[Daniel Browning]

We did a filmout test of some H.264 shot in a Canon camera, when shot we underexposed about 1/2 to 1 stop to save the highlights.

You mean in addition to HTP, right? Highlight Tone Priority sets the ISO to one lower than what is indicated on the camera (ISO 200+HTP is actually ISO 100 with -1 EC in the meter) and then does a nonlinear digital push in-camera to bring the brightness back up while preserving highlights. This increases the headroom from 3.0 stops to 4.0 stops before compression and other processing, so it's definitely much better than doing the same in post. However, sometimes you need 5 or more stops, so you need more than HTP.

Just FYI.

 

[Stefan Scherperel]

I usually under expose high contrast scenes by setting my ISO to 500 or 640, and checking back and forth between raw view and camera view. This allows me to have a scene that I can still see, and focus on, while still protecting my highlights in RAW.

 

[Jason Murphy]

Is this method only doable on film and digital raw?

Chris: Note that unless you REALLY know what you're doing, you don't want to underexpose film; it's a completely different beast to shoot than digital. Unlike digital, if you underexpose film, you run a very real risk of losing significant shadow detail because of the way film reacts to lower light levels. It takes a certain amount of light to register an image at all on film in the toe of the exposure curve. And it's much easier in most cases to correct for overexposure than underexposure in film. The opposite, of course, is true in the digital (or if you're in the increasingly rare position of shooting reversal film, which is its own beast entirely).

Film has plenty of highlight protection. It's the shadows you need to worry about. Digital is generally the exact opposite.

Of course, if you really know what you're doing, disregard everything I just said. Gordon Willis is considered one of the greatest living cinematographers for precisely this reason.